ProTF2.com always has bots, avoid. Actually generally just avoid any servers that are all grouped as the same host/website/community/whatever if there are a lot of them (like 5 or more). Most of the time you just get bots. Usually the player count appears to be 23/24 every time as well.
There's some console command to check who's a bot, but I forgot what it is. Easy ways to tell if there are bots:
1. People are taunting waaaay too often and in situations where no sane person would ever taunt.
2. The medics on your team are retarded
3. No one is a sniper or spy (servers with real players always have like 20 snipers and spies I swear)
4. People don't act like idiots while waiting in the spawn room for the game to start. Bots tend to just stand there, spam taunt, and charge up ubers. Real players will jump around randomly, stand in odd spots (spy especially), shoot each other, try to light the other team on fire as a pyro, suicide taunt with soldier, zoom in on enemy team players as a sniper, spam the "Spy!" voice command, etc etc